1. Field of the Invention
The present invention relates to a piezoelectric actuator which deforms a piezoelectric material layer by applying an electric field to the piezoelectric material layer, a liquid transporting apparatus which includes the piezoelectric actuator, and a method of manufacturing the piezoelectric actuator.
2. Description of the Related Art
In US Patent Application Laid-open No. 2006082619 (corresponds to Japanese Patent Application Laid-open No. 2006-093348), an ink-jet head which transports an ink to nozzles, and jets the ink onto a paper from these nozzle has been disclosed. This ink-jet head includes a channel unit in which ink channels including pressure chambers which communicate with the nozzles are formed, and a piezoelectric actuator which causes the ink to be jetted from the nozzles by changing a volume inside the pressure chambers.
The piezoelectric actuator includes a vibration plate which covers openings of the pressure chambers, a piezoelectric material layer which is formed on a surface of the vibration plate, and subjected to a polarization process such that the piezoelectric material layer is polarized in a direction of thickness thereof, and an individual electrode which is formed on a surface of the piezoelectric material layer, on a side opposite to a side of the vibration plate, in an area slightly smaller than an area facing the pressure chamber. The vibration plate is kept at a ground electric potential, and functions as a common electrode. In other words, an active portion, of the piezoelectric material layer, sandwiched between the individual electrode and the common electrode is positioned at a central portion of the piezoelectric material layer facing the pressure chamber.
In the abovementioned piezoelectric actuator, when a predetermined driving electric potential is applied to the individual electrode, an electric field is generated in the active portion, of the piezoelectric material layer, sandwiched between the individual electrode and the common electrode; and the active portion is contracted in a direction orthogonal to a direction of thickness thereof. Moreover, due to the contraction of the operation portion of the piezoelectric material layer, a first portion, of the piezoelectric actuator, corresponding to the operation portion positioned at the central portion of the piezoelectric material layer facing the pressure chamber, is deformed spontaneously to form a projection toward the vibration plate; and a second portion, of the piezoelectric actuator, surrounding the first portion is deformed passively due to the first portion. Accordingly, an entire portion of the piezoelectric actuator, facing the pressure chambers is deformed to form a projection toward the pressure chamber. Due to the deformation, the volume inside the pressure chamber is decreased, and a jetting pressure is exerted on an ink in the pressure chamber.